| abstract |
A protecting film for an optical recording medium consisting of a single transparent film made of a thermoplastic resin, having a retardation at a 550 nm wavelength of 15 nm or less, a K value at a 550 nm wavelength of 40 nm or less, a glass transition temperature of 120 DEG C or higher, and a water absorption coefficient of 1% by mass or less, wherein the K value is a value calculated from K=[nz-(nx+ny)/2]xd where nx, ny and nz are three dimensional refractive indexes at directions of x-axis, y-axis and z-axis of the transparent film, and d is the thickness of the transparent film. Also, an optical recording medium comprising a recording layer and said protecting film on a substrate, in which a light is incident from the protecting side of the medium. |